Anyone know of a sensor loupe made for use with mirrorless cameras? All I see are designed for dslrs, and don't focus well on the closer sensor in mirrorless bodies. Or are there any on which focus can be adjusted?
I don't have the answer you are looking for, but even on DSLRs I never found sensor loupes to be of much use. Looking for specks and mucking around and trying to clean them up individually is tedious at best and often produces new smears and other issues. Simply wet cleaning the whole sensor nearly always produces better results and is much easier.
The best loupe with the most magnification is just a picture of a plain white surface, like an evenly illuminated sheet of paper, taken fairly close at a small aperture with the lens focused at infinity. Just flip the image horizontally to have a true picture of where the nits are when you're looking at the sensor through the lens mount opening.
Different strokes, so to speak. My experience has been the reverse - using a loupe made it easier for me. Managed with the one I have by holding it up a bit from the lens mount (but then can't see the whole sensor) but now it's conked out, thus looking for a new one, hopefully more suitable.
This new one from Visible Dust claims you don't rest it on the camera mount like the older model so it should work from mirrorless bodies. Since the sensor depth is different for many brands, I think the holding off method will be the way it works unless they build brand specific loupes. 10% off right now.
FWIW, I still use my old Visible Dust 7x sensor loupe and hold it off the mount to get it focussed.